Two-speed sander



Feb. 17, 1942. E. L. CONNELL TWO-SPEED SANDER- Filed July 11, 1940 2Sheets-Sheet l INVENTOR ATTORNEY Patented Feb. 1942 'rwo-srnap ssnnnn fEdwin L. Conneil, Cleveland, Ohio, wig nor to Chicago Pneumatic ToolCompany New York, N. Y., a corporation of New Jersey Application July n,1940, Serial No. 344,907

v 8 Claim. This invention're'lates to change-speed mechanism and hasparticular application to portable power driven tools having a rotarydriving ele-- ment movable at a constant speed.

invention, a pair. or independently rotatable and controls therefo Fig.2 is a wiring diagram of a reversible motor,

in conjunction with the mechanism of the invention;

transmission gears, a free wheel clutch permitting;

the gears to transmit 'rotationzto ad'ri enelement only duringrotation-iofthefg' tion; and a driving element-rotate: directions andacting to 'dri'ge the mission gears in opposite; direction:

the tool is capable of two dinerent one of It is desirable that tools ofthis class be capable a Fig. 3 is a fragmentary plan view of the handleof operation at more than one speed since a single portion of the toolillustrated in Fig. 1, showing tool may then be conditioned for use invarying the operating controls inelevation and the reclasses of workmerely through interchanging of maining parts in section; the workperforming implements. A common Fig. 4 is a view of the transmissionmechanism sequence of operationsto which the multi-speed m in crosssection, and is taken substantially along tool is adapted, is thesanding of a rough unthe line l4 of Fig. 1, showing the parts as theyfinished surface by an abrasive disc, followed by appear during lowspeed operation;

a bufling or polishing of the surface by a working Fig. 5 is a detailview in cross section, taken implement appropriately constructed forthat substantially along the line 5-5 of Fig. 1, showpurpose. Suchsanding and polishing operations ing the manner in which the low speedgear is are most eiiiciently performed at different motor clutched tothe driven shaft during low speed speeds and ordinarily require the useof separate operation; tools geared to respective fixed speeds. Fig. 6is a view similar to Fig. 4, showing the One object of the invention isto permit a parts as they appear during high speed operation. changefrom one speed of tool operation to an- 20 the high speed gear being nowclutched to the other without the necessity of manual gear shiftdrivenshaft and the low'speed gear being ining. efliective; and I Anotherobject of the invention is to effect a Fig. '7 is a view similar to Fig.5, showing the change in the speed ratio between a power operlowspeedgear and its associated clutchmechaated driving element and adriven element by 25 nlsm as they appear during high speed operation.changing the direction of rotation of the driving The invention isdisclosed as embodied in an element. electrically powered tool of thetype commonly A further object of the invention is to transmit used insanding, grinding, polishing and like opthe rotation of a drivingelement to s. driven erations. As shown in Fig. 1, this tool is arelaelement through a selected one of two independ- 30 tively small andlight unit which may be carried ently operable transmission means,alternatively in the hands of the operator, when in use, or effective inaccordance with the direction of romanipulated while suspended from anoverhead tation of the driving element. support. The work performingelement, in the In carrying out the above objects there has presentinstance a sanding disc is supported been provided, in the presentembodiment of the at he front en of he l. and is given a rap rotatingmotion when applied to the work. The tool is adaptable for use with avariety of kinds and sizes of work performing elements, these ele- 1ments being-selectively used according to the requirements of the workto be done.

- Thestructure of'the tool includes a motor "housing ii, to therespective front and rear ends to each other. In this'jconstruction;therefore',

ofwhich are secured auxiliary housing sections I! and II. The severalhousing sections are aenwhich is obtained by rotation of the drivingeleerally circular and cooperate to form an elongated ment in onedirection, and the other or which tubular shaped assembly. The outer endof front is obtained by rotation of the driving element in section I2 isbent at right angles to the longithe opposite direction. tudinal axis ofthe housing assembly and sup Other objects and structural details of theinports a spindle to which the d g disc 1| vention will be more apparentfrom the following is secured. The flat lower face of the disc I.description when read in conjunction with the may thus be applied to thework while the tool accompanying drawings, wherein: is held naturally ina position generally parallel Fig. 1 is a view, in longitudinal section,of a to the work. '1he outer end of rear housing sec! portable sandingtool embodying the mechanism tion I8 is reduced in diameter to form agrip of the invention;

portion.or.handle,iil. Jicable ",kadingfrom r, of a type capable ofnse asource of electric current, extends into the handle 15, and separatesets of conducting lines l1 and I8 within the cable are connected torespectlve switches 19 and 21. (see also Fig. 3) of a dual switchmechanism contained within the housing l3. Supply lines extend from thewell known mode'of operation of this type clutch switches l9 and 2| intothe housing II and are connected to an electric motor supportedtherein.- The motor comprises the usual stator 22, rigidly supported bythe housing H, and rotor 23 keyed, or otherwise fixed, to a shaft 24rotatably mounted in bearings 25 and 26. The bearings 25 and 28 arelocated at opposite ends of the housing ll, the bearing 25 beingpreferably positioned in a spacing plate 21 secured between the motorhousing and front housing section [2. Under the control of the dualswitch mechanism current supplied to the electric motor may be sodirected as to effect either a right hand or left hand direction of.rotation of the rotor 23. That is, the motor is reversible. Conventionalmeans may be provided for controlling operation of the motor and onesuch means is later briefly described.

The shaft 24 extends forwardly through the spacing plate 21 intocooperative relation with a transmission mechanism whereby the rotarymotion of the shaft is transmitted to the spindle l4. Included in thetransmission mechanism is a stub shaft 28 having fast on its outer end abevel gear 29 meshing with a similarly shaped gear II on the inner endof the spindle H. The shaft 28 lies parallel to the shaft 24 and isrotatably mounted in bearings 32 and 33, respec tively positioned in thehousing l2 and front face of spacing plate 21. The front end of thedrive shaft 24 is formed as a toothed pinion 34 and is in constant meshwith a gear wheel 35 loosely mounted on the shaft 28. The gear wheel 35and pinion 34 are encircled by the flange 36a of a second gear wheel 36also loosely mounted on the shaft 28. The inner periphery of the flange36a is formed with gear teeth in substantially the same vertical planeas the gear 35 and likewise in constant mesh with the pinion 24.Referring also to Figs. 4 and 6, the pinion 34 thus lies between thetoothed surfaces of the gear wheels 35 and 36 and acts, during rotationof the drive shaft 24, to turn the gears in opposite directions withrespect to each other. It will further be evident that by reason of thedisparity in size-of the gears 35 and 38 their cyclical speed 'ofoperation differs. In a commercial embodiment of the invention,approximately 5.4 revolutions of the shaft 24 are required to turn thegear 38 through one cycle of operation whereas a. com-- plete turn cfthe gear 35 is effected in about 3.4 revolutions of the drive shaft.

The gear wheels 35 and 36 are disposed on the shaft 28 between thebearings 32 and 33 and are prevented from longitudinal movement alongthe shaft by extension of the hub of gear 36 into contact with thebearing 32 (see Fig. 1) and the provision of washers 31 and 38 whichrespectively maintain contact between the hubs of the two gears andbetween the gear 35 and the bearing 33. Although not fixed to the shaft28 the gear wheels 35 and 35 may be operatively connected theretothrough a free wheel clutch mechanism acting to transmit rotation onlyin one direction. Thestub shaft 28 is formed with a plurality oflongitudinal groove or recesses 39 (Figs. 4-7), 1

in its outer surface, adapted to receive separate sets of rollers 41 and42, the two sets of rollers being separated by the washer 31. Therollers 4| and 42 are normally seated in the deepest portion directionof rotation of the shaft 24.

, set of rollers 4! or 42 to become wedged between the gear hub and moreshallow portions of the grooves 39, and thereby connect the stub shaftto the drive shaft 24. Since the gear wheels 35 and'36 always rotate inopposite directions with respect to each other, the sets of rollers 4iand 42 are alternatively effective in accordance with the With the shaft24 turning in a clockwise direction, as shown in Fig. 4, the gear 35 isdriven in a counterclockwise direction, and is hence ineffective whilethe gear 36 is driven in a clockwise direction and shifts the rollers 42(see Fig. 5) to transmit the motion of shaft 24 to the shaft 28. Withthe shaft 24 turning in a counterclockwise direction, as shown in Fig.6, the above condition of operation is reversed, the gear wheel 36 beingnow ineffective (see Fig. 7) and the gear wheel 35 effective. Thedirection of rotation of stub shaft 28 is the same irrespective of thedirection in which shaft 24 is turned, but the speed of rotation of thestub shaft varies as the driveis effected through gear 25 or gear 36. InFigs. 4' and 6, the arrow 43 and 44 are indicative of the speed anddirection of the shaft 24 and shaft 28, respectively. The arrows 43illustrate the fact that shaft 24 is reversible and operates at aconstant speed, while the arrows 44 indicate that the shaft 28 rotatesonly in one direction but at different speeds. In Fig. 6 the shaft 28 isbeing driven through gear 35 and the arrow, in this figure, isaccordingly lengthened to show that the stub shaft moves at a greaterspeed at this time than when driven through gear 36, as is the case inFig. 4. It may be said that the shaft 28 is operating at high speed inFig. 6 and at low speed in Fig. 4.

It is desirable that the means for controlling the motor be simple inoperation and easily accessible in order that a change from one speed toanother may be made quickly and without confusion. Preferably, the motoris of the serieswound, commutator type, for use with either direct oralternating current. The present control means includes the separateswitches 15 and 21 which are alternatively operable and so arranged asto reverse the connections between the rotor 23 and the coils of thestator :22. A simple reversing circuit is shown diagrammatically in Fig.2, and is illustrative of a type of motor con trol system which may beused in conjunction with the mechanism of the present invention. Thecircuit is self-explanatory and it will be noted that each switch wand2i connects the motor to the source of supply in addition to controllingthe direction of flow of the current. Thus, to initiate operation of themotor and effect rotation of the rotor 23 in a desired direction it isonly necessary to operate a selected one of the switches and 2i. InFig.2 the switch i 5 is shown operated, or in closed position, with theresult that the current flows through the main windings of the stator:22 in the direction indicated by the adjacent a1- row in full lines. Thearrow in. broken lines indicates the direction of flow when switch 2| isclosed.

As shown in Figs. 2 and 3, the switches l9 and 21 have respectiveoperating arms 45 and 45 extending rearwardly therefrom and connected toassociated plunger 41 and 48. The pair of plungers 41 and 48 arearranged parallel to one another and extend transversely through thehandle IS, with their opposite ends projecting outside the handle inposition forflnger-tip con-= trol by the operator. Upon depression ofthe plunger 41 the switch is is actuated to obtain one direction ofrotation of the motor shaft 24 and one speed of operation, whiledepression of the plunger :33 serves to actuate the switch 2i andthereby obtain an opposite direction of rotation of shaftit and adifferent speed of operation of spindle i t. Toprevent operation of bothplungers 41 and 83 at the same time an interlock between the plungers isprovided. This interlock is in the form of a conventional ball lock inwhich apair of ball-like elements 49 are disposed in a channel 5ibetween the plungers. The locking balls 49 are shiftable within thechannel 5| and coact with slots 52 in the plungers 41 and 48 to preventmovement of one or the other of the plungers. Thus, when plunger 41 ismoved to the depressed position shown in Fig. 3, the balls 49 are cammedout of the path of the descending plunger and pressed into the slot 52in plunger 48. The plunger 48 is,thereby locked in its upper, ornon-operated, position and cannot be depressed until plunger 'l isreturned upward.

What is claimed is:

l. In a device of the class described, the combination of a drivenelement, a driving element rotatable in opposite directions,transmission means intermediate said driving element and said drivenelement, means comprised in said transmission means for effecting achange in speed ratio between said driving element and said drivenelement in response to a change in the direction of rotation of saiddrivingelement, said last mentioned means including a pair of gearsrotatable in opposite directions relatively to each other by saiddriving element each at a different cyclical speed, and clutch meansrendering each of said gears effective to transmit rotation to saiddriven element in one direction only.

2. In a device of the class described, the com-' bination of a rotatableshaft, two gear wheels of .different size rotatable independently ofeach other and mounted on said shaft, clutch means connecting said gearwheels and said shaft and permitting said gear wheels to drive saidshaft only during rotation of said gear wheels in one direction, and areversible driving gear meshing with said independently rotatable gearwheels in such manner as to effect rotation of said wheels in oppositedirections with respect to each other and at diderent cyclical speeds.

3. In a device of the class described, the combination of a rotatableshaft, two gear wheels of different size rotatable independently of eachother and mounted on said shaft, a free wheel clutch connecting saidgear wheels and said shaft and permitting said gear wheels to transmitrotation to said shaft only during rotation of said gear wheels in onedirection, the structure of said clutch including an independent set ofrollbination of a rotatable shaft, a first gear wheel rotatably mountedon said shaft and having an internal row of gear teeth, a second gearwheel rotatably mounted on said shaft and having an external row of gearteeth, clutch means connecting said gear wheels and said shaft andpermitting said gear wheels to drive said shaft only during rotation ofsaid gear wheels in one direction, rotatable driving means engaging theinternal row of teeth on said first gear wheel and the external row ofteeth on said second gear wheel and acting thereby to turn said gearwheels in opposite directions with respect to each other, and areversible motor for operating said driving means.

5. In a device of the class described, the combination of a reversiblerotary motor, a driving gear operated by said motor, a. driven shaftarranged parallel to the longitudinal axis of said driving gear,transmission means intermediate said driving gear and said driven shaftincluding a pair of gear wheels loosely mounted on said driven shaft andmeshed with said driving gear in such manner as to enforce turning ofsaid wheels in opposite directions with respect to each other, and adriving connection between said pair of gear wheels and said drivenshaft adapted to transmit rotation in one direction only.

6. In a device of the class described, the combination of a reversiblerotary motor, a driving gear operated by said motor, a driven shaftarranged parallel to the longitudinal axis of said driving gear,transmission means intermediate said driving gear and said driven shaftincluding a. pair of gear wheels loosely mounted on said driven shaftand meshedwith said driving gear,

gear operated by said motor, a driven shaft, a

first gear wheel rotatably mounted on said driven shaft and having aninternal row of gear teeth meshing with said driving gear, asecond gearwheel rotatably mounted on said driven shaft and having an external rowof teeth meshing with said driving gear, said first and second gearwheels being thereby constrained to turn in opposite directions, and adriving connection between said first and second gear wheels and saiddriven shaft adapted to transmit rotation in one direction only. Y

8. In a rotary tool having a reversible driving shaft and a drivenshaft, variable speed transers for each of said gear wheels, and areversible mission between said driving and driven shafts comprising aninternal gear and a spur gear both mounted on said driven shaft, a.driving gear operated by said driving shaft and meshed with saidinternal gear and spur gear in such manner as to effect rotation of saidgears in opposite directions relatively to each other, and meansestablishing a driving connection between said internal gear and saiddriven shaft during rotation of said driving gear in one direction andestablishing a driving connection between said spur gear and said drivenshaft during rotation of said driving gear in the opposite direction.

EDWIN L. comrsrn.

